The effects of histone acetylation and histone phosphorylaton upon histone structure, nucleosome stability, and histone-nonhistone interactions will be investigated. The objective is to provide a molecular basis to relate histone metabolism to transcription, cell proliferation, and chromosomal condensation. Different acetylated forms of H3 and H4 will be purified from calf thymus; the different phosphorylated forms of H1 and H3 will be purified from synchronized Chinese hamster (CHO) cells. The modified histones, themselves, and in vitro sytems, constructed with the in vivo modified histones, will be studied. It will be determined if "inner histone" modifications affect histone folding, histone complexing, and the stability of nucleosomes in reconstituted histone-DNA complexes. Ambient temperature circular dichroism (CD) or CD and absorbance melting profiles will be measured for appropriate samples. Deoxyribonuclease I will also be used as a nucleosome probe. The CHO cell system will serve as a model to relate the cell-cycle phosphorylations of H1 to H1 structure and H1 HMG interactions. CD and sedimentation measurements will be undertaken to test if H1 phosphorylation affects H1 structure, if it causes H1 aggregation, or if phosphorylation modulates the interactions and properties of H1 HMG complexes. Fluorescence polarization will be used for some measurements of H1 HMG complexes. A more detailed picture of the temporal changes in histone structure and chromosomal interactions would contribute to understanding the cellular mechanisms underlying cancer and tissue regeneration.